Pluto still has its supporters, however, and one of the strongest is Cara Lucy O’Connor, a six-year-old student of Glasheen Girls’ School in Glasheen, Co Cork.

She decided to write to some significant people in the astronomy world demanding that they make Pluto great again by reinstating its position as the ninth planet in our solar system.

She wrote: “I listened to a few songs about Pluto as well, and in one of the videos people were dressed as different planets, and Pluto was put in the trash can and was scared by planet Earth. This was really mean because no one or no planet or dwarf planets should be put in the trash can.”

She also told Nasa that she would like to become an “astronaut and work for ye but you need to fix this problem for me”.

She wrote to Nasa more in hope than expectation of getting a response, but she did get a reply from Dr Carly Howett, a senior scientist on the New Horizons spacecraft.

Dr Howett said it was great for young people, “especially girls”, to be interested in the planets.

She explained that there were divided views on whether or not Pluto should be planet but, she suggested, what’s in a name?

“I think Pluto is very important, but Pluto probably doesn’t care what silly people on the Earth call it. So I just call it my favourite world and let other people argue about it.”

Nasa’s New Horizons space probe in 2015 found Pluto was not an inert icy world as many had expected, but a fascinating landscape of mountains created by water ice and glaciers by frozen nitrogen.

Dr Howett then passed on Cara’s letter to Dr James Green, the director of Nasa’s Planetary Science Division.

He wrote back and also complemented her on her interest in Pluto. It was, he wrote, not a “boring cratered rock” but a “fascinating world that appears to be constantly changing”.

Strictly speaking, the decision to restore Pluto’s status as a planet would be for the IAU and not for Nasa, but, as the foremost space agency in the world and the one that sent the New Horizons probe to Pluto, it would have great influence on any reclassification.

However, Dr Green was non-committal on that point. “To me, it’s not so much about whether Pluto is a dwarf planet or not: it’s that Pluto is a fascinating place that we need to continue to study.”

The correspondence has been published in this month’s edition of Astronomy Ireland magazine.

Cara’s ambition is to discover her own new planet. She intends to call it Planet Unicorn.

The IAU downgraded Pluto having discovered an even bigger object in the outer reaches of the solar system, pointing to the possiblity that there could be dozens of Plutos out there waiting to be discovered.

In addition, the IAU determined that Pluto did not exercise sufficient gravitational heft in its corner of the sky to continue as the ninth planet.